This invention relates to improvements in remotely controlled actuator mechanisms requiring two modes of motion and, more particularly, concerns an improved push-pull cable transmitter-receiver system for shifting gears in a vehicle transmission by operation of a gearshift lever remotely in the cab of the vehicle. The invention is herein illustratively described by reference to its preferred embodiment so applied; however, it will be recognized that certain modifications and changes with respect to details may be made without departing from the essential features involved.
In the use of flexible, coaxial push-pull cables to operate mechanisms by remote control, cable friction and backlash (i.e., lost motion) are important factors as is directness in the maximum utilization of available forces in producing motion under load in the receiver unit in response to forced motion of a control member in the transmitter unit. Where two modes of motion are required, as in the case of a vehicle transmission gearshifter mechanism, a minimum of two cables is necessary for the task. An object of this invention is to provide a system of mechanical remote control in which each mode of remote control motion is produced by one of the cables while the other cable remains substantially stationary, thereby reducing both friction and backlash, in contrast to prior art systems that function through both cables simultaneously actuated and wherein friction and backlash are cumulative from both cables. A related object is to achieve the foregoing objective by transmitter and receiver mechanical units that are simple, efficient, durable and direct in the conversion between cable member motion and transmitter control member motion and receiver controlled member motion, respectively.